Low-voltage protective means



p 0- E. w. SEEGER LOW VOLTAGE PROTECTIVE MEANS Filed April 30. 1928 A 9 m 5 6 l 1. 3 EWH L A Z A L 9 w 6 Jvm wu l I w w 11v VENTOR 544mm 7.0 330W A Trolcvfi Patented Sept. 16, 1930 UNITED STATES PATENT, OFFICE EDWIN W.'SEEGEB,LOF wAUwArosA; WISCONSIN, .ASSIGNOR, BY mEsNE AssIGNmENTs,

- TOICUTLEB-HAMMER, me, A. com'omrro or DELAWABE' Low- O TAGE rRoTE o'rrvE'mEANs Application filed April 30,

This invention relates to improvements in low voltage'protective means for electric circuits. 4

An object of the invention is to provide improved protective 'means especially advantageous for phase failure protection of syn-' chronous motors and rotary converters.

A further object is'to provide simple and efficient protective means for the aforementioned and other uses which will reset automatically. v

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates diagrammatically one embodiment of theinvention which will now be described, it being understood that the embodiment illustrated is capable of various modifications and other uses falling within the scope of the appended claims.

Referring tothe drawing, there is illustrated a motor M to be connectedto a three phase alternating current circuit L L, L through a three pole elect-ro-responsive main switch 1, said main switch being under the control of phase failure protective means hereinafter described. i

The motor M may be assumed to be of the synchronous type and hence capable of operating single phase unless protected thereagainst. However, it is to be understood that the motor might be of other types.

The protective means includes three relays 2, 3 and at of like construction, each comprising an armature 5 pivoted at 6 and carrying at its lower enda contact 7 to engage a stationary contact 8, said armature being under the control of two electromagnets 9 and 10.

I The electromagnets 9 and 10 are arranged with respect to the pivot of the armature to exert opposing pulls on said armature whereby electromagnet 10 tends to hold the contacts 7 and 8 in engagement while electromagnet 9 tends to disengage said contacts.

"As illustrated the contacts 7 and 8 normally engage under the influence of gravity and hence the electromagnet 9 must overcome such bias of the movable contact and the opposing pull, it any, of electromagnet 10 in order to disengage said contacts.

until the motor stops.

1952s.; seriaiNo. 273,988.

to be included inseries with the motor and each relay isso designed as to remain closed pending failure of the phase in which its winding 10 is connected or a given reduction lnvoltage' More particularly, relay-2 has its winding 9 connected to line 'L and its winding 10. connected to line "L through w nd ng 9 of relay 4, whereas relay 3 has its w1nd1ng9 connected to line'L and its wind ing 10 connected to line L through winding 9 of relay 2 and relay 4 has its winding 10 connected to line L through winding 9 ofrelay 3, winding 9 of relay 4 being connected to line L as previously stated;

Thus assuming closure of main switch 1 and further assumin normal voltage of each phase, each relay wi 1 be held closed against the pull of its respective winding 9 whereas failure of any phase will release the'relay having its winding 10 connected therein and i such relay will then openif the phase inoludmg its winding 9 isstill supplied with a given voltageeither from the source of supply or from the motor when operating single phase; In other words, failure of one or two phases will insure operation of one or another of said relays and, as will appeanop'ening of any one of the relays will effect opening of the main switch. l Also as will appear,-fail'ure of all phases will eflect opening'of the main switch without dependence on operation, of p either relay provided the failure Tracingtheenergizing circuit of the main switch 1, the same extends from line L through relay 2 by conductor 12 through relay 3 by conductor 13 through relay t by con ductor 14 through push button switch 15 when closed, to and through the winding 16 of main switch 1 by conductor 17 to line L.

Push button switch 15 thus serves to energize the main switch assuming closure of all relays, and the main switch upon responding shunts the'push button switch. This shunt may be traced from conductor 14 by conduccontinues tor 18 through auxiliary contacts '19 of main i switch 1 by conductor 20 to a point between push button switch 15 and-the main switch winding 16, and as will be apparent this shunt provides a maintaining circuit for the main switch inclusive of relays 2, 3 and 4 in series.

Thus as previously stated, opening of any relay will deenergize the main switch, whereas failure of all phases for a period sufficient to effect stopping of the motor will deenergize the main switch independently of the re lays and the main switch in opening will interrupt its maintaining circuit. Accordingly the main switch upon opening will remain open pending depression of push button switch 15 but with the arrangement disclosed the relays upon opening will reclose auto; matically upon opening of the main switch for all relay windings will then be disconnected from circuit Aswill be understood, the relays may be designed and adjusted for the V desiredsensitiveness of response upon phase failure, as for example immediate response when the current in the live phase attains 100% value, and as will. further; be understood, the relays may be :modified' to require manual resetting thereof if desired. 7 i

hat I claim asnew and desire to secure y Letters Patent s: i

. 1. The combination with an electric circuit'having at least three lines, of low voltage protective means therefor comprising a plurality 'of relays, each having windings subjecting the same to opposing pulls and each having its windings connected to different lines ofsa-id circuit. I d

2. The combination with an electric circuit having at least three lines, of low voltage protective means therefor comprising a plue rality of relays, each biased to a given posi tion and each having a holding winding connected to one of said lines and an operating winding connected to another of saidlines.

3. The combination with an electric circuit having at least three lines, of low voltage protective means therefor comprising a switch controlling the continuity of said circuit and a plurality of, relays responsive separately to effect. opening of said switch, eachpf said relays having windings subjecting it to opposing ;pullsan'd each having its windings connected to different lines of said, circuit.

A. The combination with an electric circuit having at least three lines, of low voltage protective means therefor comprising a plurality of relays, one for each of said lines, each of said relays having an operating winding and an opposing holding winding and each having its windings connected to different lines of said circuit with its operating winding in series with a holding winding of a second relay and its holding winding in senies with the operating winding of, a third re ay. I r

5. The combination with an electric circuit having at least three wires to afford a -plurality of phases, of means to insure interruption' of said circuit upon failure of less than all phases thereof and comprising separate relays for the different phases, each of said relays having an operating winding included in one phase and an opposing holding windingconnected in a difit'erent phase.

6. The combination with an electric circuit having at least three wires to afford a plurality of phases, of means to insure interrnption of said .circuit upon failure ofless than all phases thereof, and comprising separate relays for the different phases, each of said relayshavingan operating winding and an opposing holding winding, and each having its windings connected in different 1 phases with its operating winding in phase with the holding winding of a second relay and its holding winding in phase with the operating winding of a third relay,

in phase failure protective means for. circuitshaving at leastthree Wires to afford a plurality .of phases, the combination with a main switch controlling the continuity of the several phases, of a plurality of relays separately responsive to effect opening of said main switch, each of said relays having an operating winding and an opposing holding winding connectedin different phases.

, 8. In phase failure protective means for circuits having at least three wires to afford a plurality of phases, the combination with a main switch controlling the continuity of the several phases, of a'plurality of relays separately responsive to efiect opening of said main switch, each of said relays havingan operating windingand an opposing h0lding winding connected in different phases with its operating winding in phase with a second relay I and its holding winding in phase with the operating winding of athird relay. V f

In witness whereof, I have hereunto subscribed my name. 7

' EDWIN W. SEEGER, 

